الفهرس 
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Abstract
Expansive soils are located all over the world. This type of soil is characterized by its high
sensitivity to water content. As water is introduced, its volume increases resulting in swelling.
This swelling is mainly due its content of active clay minerals such as montmorillonite,
which is responsible for the pronounced vol1!me change capability of this type of soil.
Although piles are one of the profound foundation solutions in expansive soils, little
documented data on pile and soil heave are available in such soils. Only two case studies of
full and small-scale piles could be found in the literature, namely: TRACON in Colorado, and
ELFAO in Sudan. In the current thesis, both cases are modeled by the finite element software
ADJNA.
Modeling of the two cases by ADINA software is performed by the critical state model;
Cam-Clay. A wide search and numerical trials are conducted to choose the Cam-Clay model
parameters published in expansive clay cases, where four sets are selected. These sets are
employed in modeling the two Case Studies. Results show that the so-called Weald Clay set
gives the best agreement between measured and computed pile heave, which is encountered
in the numerical study of piles.
A numerical study of an axi-symrnetric single pile in ’expansive soil exposed to inundation
over ground surface is presented to clarify the effect of some pile and soil variables on pile
heave. A belIed pile of same soil and pile properties is also mode led, where comparison
between induced heave of the two techniques is presented. In addition to the single pile, pile
group of straight and belled piles are also modeled.
On the assumption of fully saturation of the expansive soil, results show that pile length is
superior over pile diameter in controlling the pile heave. That is as pile length increases,
heave effectively decreases. Also, belled piles depict effect on reducing the heave. Pile
groups reduces the heave effectively, however no considerable difference is noticed between
straight and belled pile group in reducing the heave
Inundation in expansive soil results in tensile stresses within pile. Loading of pile effectively
mitigates these stresses. Results indicate that Increase of the compression loading on the piles
reverses the induced tensile stresses into compressive ones.